iommu/intel: announce supported page sizes

Let the IOMMU core know we support arbitrary page sizes (as long as
they're an order of 4KiB).

This way the IOMMU core will retain the existing behavior we're used to;
it will let us map regions that:
- their size is an order of 4KiB
- they are naturally aligned

Note: Intel IOMMU hardware doesn't support arbitrary page sizes,
but the driver does (it splits arbitrary-sized mappings into
the pages supported by the hardware).

To make everything simpler for now, though, this patch effectively tells
the IOMMU core to keep giving this driver the same memory regions it did
before, so nothing is changed as far as it's concerned.

At this point, the page sizes announced remain static within the IOMMU
core. To correctly utilize the pgsize-splitting of the IOMMU core by
this driver, it seems that some core changes should still be done,
because Intel's IOMMU page size capabilities seem to have the potential
to be different between different DMA remapping devices.

Signed-off-by: Ohad Ben-Cohen <ohad@wizery.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>